Method of preparing unsaturated nitriles



United States Patent 3,335,169 METHOD OF PREPARING UNSATURATED NITRILESJamal S. Eden, Akron, Ohio, assignor to The B. F. Goodrich Company, NewYork, N .Y., a corporation of New York N 0 Drawing. Filed Jan. 10, 1966,Ser. No. 519,460 9 Claims. (Cl. 260-4655) This is a continuation-in-partof my copending application, Ser. No. 338,604, filed Jan. 20, 1964, nowabandoned.

This invention relates to a method of preparing acrylonitrile ormethacrylonitrile by ammoxidation of monoolefinic hydrocarbonscontaining 3 to 4 carbon atoms at an elevated temperature, and moreparticularly pertains to a method of preparing acrylonitrile ormethacrylonitrile by passing vapors of propylene, or isobutylene,ammonia and an oxygen containing gas at a temperature of from about 375C. to about 500 C. through a catalyst comprising a mixture of amolybdenum oxide, tellurium oxide and a manganese phosphate in a molarratio of 100 M00 10100 TeO and 5-100 of a manganese phosphate. Thecatalyst can also be designated as with P being in the form of aphosphate i.e. each P atom it attached to 3 to 4 oxygen atoms.

Nitriles have been prepared by ammoxidation of hydrocarbons, especiallyfrom the normally gaseous hydrocarbons. However, prior catalysts andprocedures for amnioxidizing propylene or isobutylene to acrylonitrileor methacrylonitrile have shortcomings. The catalysts either have a veryshort active life, or they convert only a portion of the hydrocarbon tothe desired unsaturated derivative per pass, or they oxidize thehydrocarbon excessively to form high proportions of carbon monoxide orcarbon dioxide or both or they are not sufficiently selective, so thatthe hydrocarbon molecule is attacked at both the olefinic unsaturationand at a methyl group, so that large amounts of HCN and acetonitrile areformed.

' It is therefore unexpected to find a catalyst that will convert fromover 50 to as high as 100% per pass of a monoolefin containing 3 to 4carbon atoms to yield very high proportions of acrylonitrile ormethacrylonitrile. A furether feature is the unusually long active lifeof the catalyst. Still another feature of the invention is concurrentproduction of acrylic and methacrylic acid in recoverable amounts alongwith acrylonitrile and methacrylonitrile.

THE REACTANTS The essential reactants are propylene or isobutylene,ammonia and an oxygen-containing gas, which can be pure oxygen, oxygenenriched air or air Without additional oxygen. For reasons of economy,air is the preferred oxygen-containing reactant.

The addition of steam into the reactor along with the monoolefin,ammonia and an oxygen-containing gas is desirable but not absolutelyessential. The function of steam is not clear, but it does seem toreduce the amount of carbon monoxide and dioxide in the eflluent gases.

Other diluent gases can be used. Surprisingly, saturated hydrocarbonssuch as propane or butane are rather inert under the reactionconditions. Nitrogen, argon, krypton or other known inert gases can beused as diluents if desired but are not preferred because of the addedcost.

THE CATALYST AND ITS PREPARATION There are several methods for thepreparation of the catalyst, which can be supported or unsupported. Itis possible to dissolve each of the starting ingredients in water andcombine them from the aqueous solutions or the in- 3,335,169 PatentedAug. 8, 1967 gredients can be dry blended. Because of'the more uniformblend obtained by the solution procedure, it is preferred.

The general procedure for preparing a catalyst from Water solubleingredients is to dissolve the requisite amount of a molybdenum salt, atellurium salt and a manganese salt in water. Add the requisite amountof phosphoric acid to the manganese salt solution. Add the telluriumsalt solution to the molybdenum salt solution and then add the manganesesalt-phosphoric acid mixture to the molybdenum-tellurium salt mixture.The catalyst is then dried and baked at 400 C. for about 16 hours.

Supported catalysts can be prepared by adding an aqueous slurry of thesupport to the aqueous solution of catalyst or the aqueous catalystingredients can be added to the slurry of the support.

Alternately a slurry of the catalyst ingredients can be prepared inwater, then dried and baked. For supported catalysts the aqueous slurryof the catalyst ingredients can be added to an aqueous suspension of thesupport or vice versa, and then dried and baked.

A third method is to blend the dry ingredients and then mix themthroroughly. The main difliculty is to obtain thorough blending anduniform particle size.

Specific procedures for making catalysts are as follows:

I. (a) Dissolve 105.96 g. of (NH M0 O -4H O in 272 ml. water at 50-55 C.

(b) Dissolve 53.76 g. NH TeO in 900 ml. water at 50--55 C. and add tothe molybdate solution with stirring. The mixture may become cloudy butno precipitate is formed.

(c) Dissolve 79.19 g. MnCl -4H O in 40 ml. water and add 46.2 g. of 85%H PO thereto.

Add the mixture described under (c) to the mixture of the ammoniummolybdate and ammonium tellurate. No precipitate is formed but the finalmixture remains cloudy.

If the catalyst is to remain unsupported, the mixture is evaporated todryness on a steam bath, heated at 150- 200 'C. for about an hour andthen about 16 hours at 400 C. Then the catalyst is cooled, ground andsieved. For fixed bed systems a 10'-18 mesh (U.S. Sieve) size is used.For fluid bed systems the catalyst should be -325 mesh (U.S. Sieve);

If the catalyst is to be supported the aqueous solution of ingredientscan be added to an aqueous slurry of the support or vice versa, prior todrying. The procedure after drying is the same as that alreadydescribed.

Thus, to the aqueous catalyst ingredients 240 g. (1.2 mols) of acolloidal silica (Ludox HS.) are added slowly with stirring. Stirring iscontinued for about /2 hour prior to drying.

II. This proceduce is a variant of Procedure I.

(a) Prepare a slurry of 43.189 g. M00 (99.5% purity).

(b) Make a slurry of 15.961 g. TeO (Technical) in water and blend with(a) above.

(0) Dissolve 39.584 g. MnCl .4H O in water and add 23.1 g. H PO Blendthis mixture with the slurry of M00 and T e0 Mix thoroughly and then dryand bake, or, if desired, add g. Ludox H.S. to the catalyst beforedrying.

Another procedure is to add the mixture described under (c) to the Ludoxand then add the requisite amount of TeO and M00 as a slurry.

Also the ingredients can be added to the Ludox individually if desired.

III. In this procedure the ingredients are precipitated on blending.

(a) Dissolve 105.96 g. of ammonium molybdate in water at about 50 C.

3 (b) Dissolve 31.922 g. TeO in concentrated HCl and filter ifnecessary.

Add the tellurium salt solution to the ammonium molybdate solution. Aprecipitate forms.

() Dissolve 79.168 g. MnCl .4H O in water and add 46.2 g. of 85% H POAdd this mixture slowly to the.

precipitated ammonium molybdate-TeO mixture.

Dry on a steam bath and bake for 16 hours at 400 C. Thereafter thecatalyst is ground to the desired mesh size and sieved. For supportedcatalysts an aqueous slurry can ganese phosphate can be used foroxidizing the mono- I olefinic hydrocarbon to nitrile and carboxylicacid. The catalyst contains chemically bound oxygen so that the genericformula can be written as 100 M00 10-100 T502, Ml'lzPzOq.

Among the suitable supports are silica, silica-containing materials,such as diatomaceous earth, kieselguhr, silicon carbide, clay, aluminumoxides and even carbon, although thelatter tends to be consumed duringthe reaction.

A useful catalyst is one having a ratio of 100 M00 33.25 TeO and 33.24Mn P O because it gives the high yields of desired products, and. thepreferred support is silica, becauseof its low cost and good fluidizingcharacteristics.

REACTION CONDITIONS The reaction can be carried out ineither a fixed orfluidized catalyst bed.

The reaction temperature can range from about 375 to 500 C. but thepreferred range is from about 400 to about 480 C. Below 375 C. theconversion of monoolefin per pass and yield of unsaturated derivativesis lower than desirable. Usually, a longer contact time is needed atlower temperatures to obtain the yields ofunsaturated nitrilesobtainable at temperatures in the Optimum range. 4

Above 480 C. some of the acrylonitrile appears to be oxidized to carbonoxides, acetonitrile and HCN. Thisis much more apparent at 500 C.

The ratio of oxygen to propylene should be from 1.5 to 1 and preferablyfrom 2 to 1 to 4m 1 for good conversion and yields, but ratios with someexcess oxygen, 33 to 100% is even more desirable and is preferred. Thereis nocritical upper limit as to the amount of oxygen, but when air isused as the oxygen-containing gas it becomes apparent that too great anexcess will require large reactors, pumping, compressing and otherauxiliary equipment for any given amount of desired end product. It istherefore best to limit the amount of air to provide 33 to 66% excess ofoxygen. This range provides the largest proportion of desired products,under given reaction conditions. Also, since care is needed to avoid anexplosive mixture the limiting of air aids in that direction. The molratio of ammonia to propylene can range from about 0.5 to 1 to about1.75 to 1. A preferred ratio is 0.75 to 1.5 of ammonia per mol ofpropylene or isobutylene. At molar ratios of m 1 of ammonia,substantial.

amounts of acids are formed, which at molar ratios of about 1 to 1.75 ormore, nitriles are the primary product. The molar ratio of steam, ifused, to propylene can range from 0 to about 8, but bestresults areobtained with molar ratios of about 3 to 5 per mol of propylene and forthis reason are preferred.

The contact time can vary considerably in the range of about 2 to 70seconds. Best results are obtained in a range of about 8 to 54 secondsand thisrange is preferred.

Satisfactory particle size catalyst for fixed bed systems is 10-18 mesh(U.S. Sieve) andfor fluid bed systems -325 mesh.

The reaction can be runat atmospheric pressure, in a partial vacuum orunder induced pressure up to 50100 p.s.i. Atmospheric pressure ispreferred for fixed bed systems and a pressure of 1 to 50 p.s.i. forfluid bed reactions. Care is needed to operate at a pressure which isbelow the dew point pressure of the acrylonitrile or methacrylonitrileat the reaction temperature. It is possible to obtain efficiencies of58.6 to 86.4% for acrylonitrile, depending on the type of catalyst, thereactant ratios and the reaction conditions. The yields and efficienciesof methacrolein from isobutylene are not as high as those of acroleinfrom propylene, but it is surprising that efliciencies of from 30.9 to48% can be obtained, because it is generally known that isobutylene ismuch more diflicult to convert to a nitrile than is propylene.

A desirable catalyst for preparing acrylonitrile is one with a molarratio of 75 M00 25 TeO and 15 Mn P O because it provides good efiiciencyin converting propylene to the unsaturated nitrile. For the preparationof methacrylonitrile a good catalyst has a molar ratio-of 75 M003, T602and Mnzpgoq.

The examples are intended to illustrate the invention but not to limitit.

Example I The catalyst in this example was prepared by Procedure IHdescribed above. It contained a molar ratioof 75 M00 25 TeO and 15MllgPzOq and was unsupported. A high silica glass (Vycor) tube 12 incheslong and 30 mm. in outer diameter was filled withv ml. of the catalyst.The reactor had three inlets, one for air, one for steam and one forpropylene. Three external electrically operated heating coils were woundon the reactor. One of the coils extended along the entire length of thereactor and each of the remaining coils extended about one half thelength of the reactor.

Outlet vapors were passed through a short water cooled condenser.Uncondensed gases were passed.through a gas chromatograph (Perkin-ElmerModel 154D) and analyzed continuously. The liquid condenser was weighedand then analyzed for its acrylonitrile content in the gaschromatograph.

Steam at a temperature of ZOO-250 C. was first passed into this fixedbed reactor. Then propylene and air were fed separately into the streamof water vapor. The mixture passed through a pre-heater and entered thereactor at a temperature of 200250 C. The reactor was preheated to about300 C. before the gas feed was begun.

The molar ratio of the feed was 3 mols of oxygen (supplied as air) permol of propylene, 4.25 mols of water per mol of propylene and 1.29 molsof ammonia per mol of propylene. The temperature in the reactor wasraised to about 440 C. and held at this temperature during the run. Thecold contact time was 38 seconds.

All of the .propylene was consumed in the reactor to produce a molpercent yield of 86.4% based on the propylene converted. The efiiciencywas also 86.4%. No acetonitrile could be detected in the eflluent gases.

Example 11 The reactor, the conditions for feeding the reactioningredients into the reactor and the volume of catalyst were the same asthose described in Example I. The catalyst had a molar ratio, of 75 M0025 TeO and 25 The feed ratio and amount of catalyst in this exampleesses for their manufacture are desired. That the same catalyst andequipment may be used to produce these two materials at the same time isof substantial economic value. As is known, more economical operationsin the process industry are generally obtained with larger equip- 5 f zzg g 2 23 gi gi g g g gg gg ggg g z g ment, and, in accordance with thisinvention, both acrylic 3 The reaction temperatureagvas and cold acidand acrylonitrile can be produced in commercial conia t iime was 50seconds. All of the propylene was amounts slml'lltanewsly m the .Sameequlpment and a converted, with a yield and efliciency for acrylonitrileof more. f be bunt and used Thus 82 5% No acetonitrfle was detected.stantial savings are obtained as compared to separate plants for makingthese two materials.

Example IV In order to obtain substantial amounts of both acrylic TheCatalyst of this example had a molar ran-O of 50 or methacrylic acid andacrylonitrile or methacrylonitrile M00 20 TeO and 5 MIlzPzOq. The amountof catalyst, tron? Propylene or lsjobutylene the m f of reactant ratios,and contact time were the same as demoma to monoolefin 18 preferablymamtamed at less than scribed in Exam pl 6 IL The temperature was Allabout 1 mol down to about /2 mol. Usually, when amounts of the propylenewas converted with a yield and efliciency of m f .greater than 1 molused the yield of for acrylonitrile of 76.1%. No acetonitrile wasdetected. acryhc decreased Substantially and the yleld of acrylonitrilehigh. In the range of about 0.4 to 0.9 mol Example V 20 of ammonia permol of monoolefin, substantial amounts, The catalyst had a molar ratioof 75 M003, o in economic yields, of both acids and nitrile areobtained. and 10 of Mn (P O The ratio of reactants, amount of A senes ofE 9 demonstrat? slmultaneous P catalyst and contact time were the sameas those of Exi of Y q and acl'ylollltflle We Ie made- In the ample II.The reaction at 422 C. converted 87.1% of the equlpmellt descflbed 1HEXEIIIIP1e I and Wlth the catalyst propylene with a yield of 74.3% ofacrylonitrile for an 25 of Example II, the results obtained in theseveral runs efiiciency of 64.7%. At 440 C., 93.67% of the propylene areset forth below.

Yield Percent Run 'Iemp., Contact NH: Conversion,

C. Time, sec. Moi Percent Acrylic Acid Acrylonitrile was converted witha yield of 86.7% acrylonitrile for an For the purpose of this inventionthe propylene and efliciency of 77.4%. 40 isobutylene hydrocarbonsemployed can be defined by the Example VI formula The ratios ofreactants and contact time were the same H as described in Example II.The reaction was run using (0119M 170 ml. of a catalyst having a molarratio of 75 M00 CHPC=CH 25 TeO and 25 (Mn) (PO At 425 0., all of thePFOPYIeHe was Converted Wlth Yleld of 645% Of rylc- It is apparent thatthe desired end products result from mmle' the reaction of only onemethyl group on the hydrocarbon Example VII molecule, while the terminalCH =C group remains In this example isobutylene was used in place ofprointact.

pylene.

The catalyst and volume thereof were the same as described in ExampleII. The data obtained are set out below.

The nitriles produced can be defined as alpha, beta monoolefinicallyunsaturated nitriles having 3 to 4 carbon atoms and a terminal CH =Cgroup or they can be defined by the general formula Contact Temp., M01Percent M01 Percent M01 Percent Oz/CiHa HaO/C4Ha NH3/C4Ha Time, C.Conv., Yield, Efficiency sec. 04H: C4H5N 3. 0 3. 35 1.46 25 460 88. 235. 0 30. 2 I 3.5 3.85 I 1.46 t 21 I 430 100 48.0 48.0

H This example shows that good yields of methacryloni- (CHQH trile canbe obtained with the catalysts of this invention. CHZ=C CN Resultsobtained in a fluidized bed are comparable and the acids as to that ofthe fixed bed. H

The yield of desired nitrile is slightly lower with sup- (CHM-1 O portedcatalysts than with unsupported catalysts in both the fixed and fluidbed procedures. 0H One of the particular and unexpected advantages ofThe method of impregnating a silicic carrier with indithe process of theinvention is the discovery that substantial amounts of acids andnitn'les, as acrylic acid and acrylonitrile, can be simultaneouslyproduced and thereafter readily separated. Both acrylic acid andacrylonitrile are important commercial materials and improved procvidualingredients of the catalyst system and thereafter combining the soimpregnated carriers to complete the catalyst preparation is disclosedand claimed in patent application No. 380,683, filed July 6, 1964, inthe name of T. L. Kang.

which comprises passing oxygen, ammonia and hydrocarbon of the formulain a molar ratio of one mol of hydrocarbon, about 1.5 to 4 mols ofoxygen and about 0.5 to 1.75 mols of ammonia over a catalyst consistingessentially of molybdenum oxide, tellu-rium oxide and a managanesephosphate in a molar ratio of 100 M -100 TeO and 5100 of manganesephosphate, at a temperature fromabout 375 C. to about 500 C. and acontact time of about 2 to 70 seconds.

2. The method of claim 1 wherein propylene, ,air, ammonia and water arepresent in a ratio of 1 mol of propylene, sufficient air to provide fromabout 2 to 4 mols of oxygen, up to about 8 mols of water, and from about0.5 to about 1.75 mols of ammonia, and the temperature is about 400 C.to about 480 C. at a contact time of 8 to 54 seconds.

3. The method of claim 2 wherein there is present about 0.75 to 1.5 molsof ammonia and 3 to 5 mols of water per mol of hydrocarbon.

4. The method of claim 3 wherein the catalyst consists. essentially, ona molar basis, of about 75' M00 25 TeO and to Mn P o 5. The method ofclaim 1 wherein the hydrocarbon is isobutylene, present with air,ammonia and water in a ratio of 1 mol of isobutylene, suflicient air toprovide from about 2 to 4 mols of oxygen, up to about 8 mols of waterand from about 0.5 to about 1.75 mols of ammonia per mol of isobutyleneat atemperature of about 400 C. to about 480 C. and a contact time of 8to 54 seconds.

6. Themethod of claim 5 wherein there is present about 0.75 to 1.5 molsof amomnia and 3 to 5 mols ofv water per mol of hydrocarbon.

7. The method of claim 1 wherein there are concurrent- 1y producedcompounds of the formula wherein the molar ratio of ammonia is fromabout 0.4 to about 0.9 mol.

8. The method of claim 7 wherein propylene, air, ammonia and Water in aratio of 1 mol of propylene, sufii cient air .to provide from about 2 to4 mols of oxygen, up to about 8 0.9 mol of ammonia per mol of .propyleneare passed over the catalyst at a temperature of about 400 C. to about480 C. anda contact time of 8-54 seconds;

9. The -metl1od of claim 7 wherein isobutylene, air ammonia and water ina ratio of 1 mol of isobutylene, sufficient air to provide from. about 2to 4 mols of oxygen, and from about 0.4 to 0.9 mol of ammonia are passedover the catalyst .at a temperature of about 400 C. to about 480 C. anda contact time of 8 to 54 seconds.

References Cited UNITED STATES PATENTS 3,009,943 11/1961 Hadley et al.260-4653 3,135,783 6/ 1964 Sennewaldet a1. 260-4653.

3,200,081 8/1965 Callahan et al. 260-465.3

FOREIGN PATENTS 1,255,121 1/1961 France.

1,269,382 7/ 1961 France.

CHARLES B. PARKER, Primary Examiner.

JOSEPH P. BRUST, Examiner.

mols of water vapor, and from about 0.4 to

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,335,169 August 8, 1967 Jamal S Eden It is hereby certified that errorappears in the above numbered patent requiring correction and that thesaid Letters Patent should read as corrected below.

Column 8 lines 6 to 11 the formulas should appear as shown below insteadof as in the patent H H (CH )O-l (CH )Ol and CH -CN 0 2 cH =c-c Signedand sealed this 24th day of September 1968. (SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

1. A METHOD OF PRODUCING COMPOUNDS OF THE FORMULA